Message Queue

A message queue is a form of asynchronous communication between services where a producer sends messages to a queue, and a consumer reads them when ready. The queue persists messages until they are consumed, decoupling the timing and speed of producers and consumers.

Message queues enable reliable asynchronous processing. When an API webhook delivers a price update, instead of processing it immediately (which could block if the downstream system is slow), you enqueue it and process it as capacity allows. If the consumer crashes, the message stays in the queue for retry.

Popular message queue systems include RabbitMQ, Amazon SQS, and Redis Streams. They differ from event streaming platforms like Kafka in that queues typically deliver each message to exactly one consumer (competing consumers), while streaming platforms allow multiple consumer groups to read the same event independently.